This invention pertains to reciprocating floor conveyors of the type having a plurality of movable slats for conveying a load and, more particularly, to a reciprocating floor conveyor having a set of slats for conveying a load and a second set of slats for lifting and holding the load while the set of conveying slats retract.
Reciprocating floor conveyors having a plurality of movable slats for conveying a load are now generally well known. They are used in a variety of applications and for conveying many different types of loads. Examples of reciprocating floor conveyors are disclosed in U.S. Pat. No. 3,905,290, of Caughey, granted Sep. 16, 1975; U.S. Pat. No. 4,709,805, of Foster, granted Dec. 1, 1987; and U.S. Pat. No. 5,088,595, of Hallstrom, Jr., granted Feb. 18, 1992.
It has been discovered that reciprocating floor conveyors do not always function well when conveying palletized loads. With palletized loads, the pallets do not always remain balanced with their weight evenly distributed on the slats. The movable slats of a conveyor contact the bottom of the pallets at various contact points about the pallets, rather than uniformly across the bottom surface of the pallets. Unfortunately, the contact points are not always evenly distributed across the conveyor slats. As a result, the advancing conveyor slats do not always advance the pallets in a uniform manner, and the retracting conveyor slats sometimes catch the pallets and rotate them. This can cause the load to become stuck or blocked on the conveyor. Consequently, reciprocating floor conveyors do not always convey palletized loads in a reliable and controlled manner.
With non-palletized loads, such as bulk material and garbage, the distribution of the load remains relatively uniform across the conveyor slats and, thus, the conveyor slats can function to convey the load in a uniform, controlled manner. However, with palletized loads, especially with older, used pallets, which can become bent or warped, the pallets contact the movable slats at certain points non-uniformly distributed about the slats. As a result, the basic concept of reciprocating floor conveyors with movable slatsxe2x80x94having more slats conveying the load than slats being retractedxe2x80x94does not always work to convey pallets and other similar type loads with fixed-form wide bases.
Accordingly, it is an object of the present invention to address the problems associated with conveying palletized loads or the like using reciprocating floor conveyors having a plurality of movable slats.
Briefly described, in a first embodiment, the reciprocating floor conveyor of the present invention comprises a support frame, a plurality of laterally spaced-apart conveyor slats mounted on the support frame for longitudinal reciprocation between xe2x80x9cstartxe2x80x9d and xe2x80x9cadvancedxe2x80x9d positions. The conveyor slats have upper surface portions with a constant vertical height that define a horizontal conveying plane. The reciprocating floor conveyor also includes a plurality of laterally spaced-apart holding slats mounted on the frame for vertical movement between an xe2x80x9cupxe2x80x9d position, in which the upper surfaces of the holding slats are above the conveying plane defined by the conveyor slats, and the articles are supported by the holding slats, and a xe2x80x9cdownxe2x80x9d position in which the upper surfaces of the holding slats are below the conveying plane and the articles are supported by the conveyor slats. The conveyor slats and the holding slats are distributed across the conveyor in a pattern resulting in both conveyor slats and holding slats being below each article on the conveyor. A mechanism is provided for raising the holding slats from their xe2x80x9cdownxe2x80x9d position to their xe2x80x9cupxe2x80x9d position to lift any articles on the conveyor up off the conveyor slats to permit the conveyor slats to be retracted from their advanced position to their start position while the conveyor slats are out of contact with the articles.
Preferably, the conveyor slats are mounted on the support frame so that their movement is restricted solely to longitudinal reciprocation, and the holding slats are mounted on the support frame so that their movement is restricted to vertical movement. In this manner, separate drive units control the movement of the conveyor slats and the holding slats. Such a design simplifies the operation of the reciprocating floor conveyor.
The holding slat support assemblies can be designed in many different ways. For one design, a holding slat base is provided for each holding slat. Each holding slat base includes a movable surface positioned to engage the respective holding slat to raise the holding slat from its xe2x80x9cdownxe2x80x9d position to its xe2x80x9cupxe2x80x9d position and lift any articles on the conveyor up off the conveyor slats. The movable surface has a variety of disclosed embodiments. An expandable member such as an inflatable lifting tube is provided between each holding slat and its holding slat base. Expansion of the lifting tube raises the holding slats away from the holding slat bases and from their xe2x80x9cdownxe2x80x9d positions to their xe2x80x9cupxe2x80x9d positions. Between each holding slat and its holding slat base, a collapsible pocket is formed in which the expandable member is located.
According to an aspect of this design for the holding slats, each holding slat includes a top, and a sidewall extending downwardly from the top, the sidewall adapted to engage its holding slat base and keep the holding slat aligned on the holding slat base. The sidewall also provides lateral support for the expandable member.
According to another aspect of the invention, a second pair of expandable members are provided beneath the holding slat base and a pair of bottom flanges extend inwardly from the sidewalls of the holding slat. Expansion of the second expandable members causes the holding slat to move downwardly. Other holding slat arrangements are provided as examples of alternative designs for the holding slats.
According to an aspect of the invention, a control arm is provided extending downwardly from one of the holding slats and a control rod is provided adjacent the control arm. The control rod controls the direction of movement of the conveyor slats. The control rod includes a pair of spaced abutments in the path of movement of the control arm. The control arm is adapted to shift the control rod between a first and second position by contacting the abutments as the holding slat moves between its xe2x80x9cupxe2x80x9d and xe2x80x9cdownxe2x80x9d positions.
According to one aspect of the invention, the movable surface of each holding slat base is a cam surface. Preferably, the cam surface is that of an oval-shaped cam member that is rotatably carried on a holding slat base to rotate and lift the holding slat as the oval cam portion engages the holding slat.
According to another aspect of the invention, each holding slat base includes a longitudinally-movable base member, and the cam surface is carried by the base member. Preferably, the cam surface is that of a wedge block or a ramp block longitudinally movable to raise the holding slat as the wedge or ramp moves beneath the holding slat. In this embodiment, a bearing is provided for each holding slat, which bearing supports the holding slat, and the movable surface engages the holding slat by engaging the bearing. Other embodiments are illustrated that include a movable surface adapted to engage and raise the holding slat.
These and other objects, advantages, and features of the present invention will become apparent from the following description of the best mode of the invention, and the accompanying drawings, and the claims, which are incorporated herein by reference.